School-age arsonists who started 183 grass and mountainside fires over four days have cost taxpayers a staggering £366,000.

The alarming figure has been revealed by South Wales Fire and Rescue Service as it gears up for a further surge in demand during the two-week Easter school holiday, which starts next week.

Divisional Officer Mick Flanagan urged parents to keep an eye on their children and to make sure they know how dangerous starting fires can be.

He said: 'Every year, grass arson places a huge burden on the resources of South Wales Fire & Rescue Service. It costs the community hundreds of thousands of pounds.

'We implore young people not to get involved and we urge parents to keep an eye out and discourage them from starting blazes.'

His call comes as the period of good weather has left the service struggling to cope in many areas.

Between midnight on Saturday and midnight on Tuesday, fire crews attended 183 deliberately started fires in South Wales, with many of them on hillsides in the Valleys.

Official figures show there were more than 300 calls over 24 hours between Monday and Tuesday evening, with the majority being to grass fires. In total this month, there have been 505 grass fires, compared to 476 over the same period in March last year.

Divisional Officer Flanagan said each call costs the service £2,000, with that figure including not only the cost of attending the incident, but also the cost of providing and maintaining fire engines and the cost of the education programme for schools aimed at combating grass arson.

He said: 'While we are out fighting so many fires on mountainsides, there are fewer units available to attend road accidents and house fires.'

Firefighters in Maesteg have been particularly badly affected since Saturday, with crews tackling 50 blazes, mostly in the Blaencaerau area.

Sub Officer Mark Samuel said on weekdays the volume of calls increases noticeably after schools finish for the day at 3.30pm.

He said firefighters had seen youngsters on motorbikes lighting a fire and riding off and lighting another 500 yards away when they arrived.